The companies argued their merger was needed to compete against the biggest wireless carriers, AT&T and Verizon, and to complete a build-out a nationwide 5G network. T-Mobile, the No. 3 USA phone company, has been known for such consumer-friendly, industry-shattering measures as abolishing two-year service contracts and restoring unlimited data plans. The so-called "megamerger" already has approvals from the FCC and the Justice Department.
After winning regulatory approvals for combining their wireless networks a year ago, T-Mobile and Sprint still had to contend with a lawsuit filed by the attorneys general of several different states.
Uniting T-Mobile's low-band spectrum and Sprint's mid-band spectrum could allow a faster roll-out of a national 5G network, the companies have said. John Legere, the outspoken CEO of T-Mobile, is leaving his post at the end of April. If the agreement needs to be amended, "including possibly price, we would handle that very swiftly after the deal was approved", he said.
New York's attorney general said the state is considering an appeal; California's attorney general said that state is "prepared to fight".
Under the settlement, Dish will be able to access T-Mobile's network for seven years as DIsh builds out its own 5G network.
After the merger, T-Mobile will have more spectrum - the frequencies through which wireless signals are transmitted - than any other carrier.
The states had said that Dish wasn't certain to succeed as a wireless company and was far smaller than Sprint, and the resulting wireless market would still be worse for consumers. Now Dish faces up to $2.2 billion in fines if it fails to create a 5G network that serves 70% of the country by 2023.
Many analysts had warned that if the merger could not go ahead, Sprint may not survive in the competitive, capital-intensive wireless services market - a view cited by Judge Victor Marrero as part of his decision in favor of the acquisition.
Attorneys general from NY and California led the case and were joined by Connecticut, Hawaii, Illinois, Maryland, Massachusetts, Michigan, Minnesota, Oregon, Pennsylvania, Virginia, Wisconsin and the District of Columbia. The combined company, which will operate under the T-Mobile name, will have a regular monthly subscriber base of about 80 million - in the same league as AT&T Inc., which has 75 million subscribers, and Verizon Communications Inc., which has 114 million. That vote could come this month, as both T-Mobile and Sprint have filed their final arguments with the state regulatory agency, but one report from late previous year suggests the decision could be pushed to the summer.
Sprint shares jumped $3.51, or 73%, to $8.31 in morning trading after the ruling came out.